root/tools/testing/selftests/bpf/progs/sendmsg4_prog.c

DEFINITIONS

1. SEC

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2018 Facebook
   3 
   4 #include <linux/stddef.h>
   5 #include <linux/bpf.h>
   6 #include <sys/socket.h>
   7 
   8 #include "bpf_helpers.h"
   9 #include "bpf_endian.h"
  10 
  11 #define SRC1_IP4                0xAC100001U /* 172.16.0.1 */
  12 #define SRC2_IP4                0x00000000U
  13 #define SRC_REWRITE_IP4         0x7f000004U
  14 #define DST_IP4                 0xC0A801FEU /* 192.168.1.254 */
  15 #define DST_REWRITE_IP4         0x7f000001U
  16 #define DST_PORT                4040
  17 #define DST_REWRITE_PORT4       4444
  18 
  19 int _version SEC("version") = 1;
  20 
  21 SEC("cgroup/sendmsg4")
  22 int sendmsg_v4_prog(struct bpf_sock_addr *ctx)
  23 {
  24         if (ctx->type != SOCK_DGRAM)
  25                 return 0;
  26 
  27         /* Rewrite source. */
  28         if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||
  29             ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {
  30                 ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);
  31         } else {
  32                 /* Unexpected source. Reject sendmsg. */
  33                 return 0;
  34         }
  35 
  36         /* Rewrite destination. */
  37         if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
  38              ctx->user_port == bpf_htons(DST_PORT)) {
  39                 ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
  40                 ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
  41         } else {
  42                 /* Unexpected source. Reject sendmsg. */
  43                 return 0;
  44         }
  45 
  46         return 1;
  47 }
  48 
  49 char _license[] SEC("license") = "GPL";